In a wireless communications system, before information is sent, a scrambling sequence is usually used to scramble the information. The scrambling sequence is generated according to a parameter such as a timeslot sequence number (Slot Number) of a timeslot included in the sent information. Generally, information is transmitted by using a data frame as a unit. One data frame includes 10 subframes, and one subframe includes two timeslots. Therefore, there are 20 timeslots in total in one data frame. A transmit end sends data at a timeslot, and a scrambling code sequence generated according to a timeslot sequence number of the timeslot is used to scramble information.
When information is transmitted, if data is transmitted on a licensed carrier, because the licensed carrier is private, a transmitted data frame is continuous, and a timeslot sequence number is also continuous; if data is transmitted on an unlicensed carrier, because the unlicensed carrier is public, the unlicensed carrier needs to be preempted for using, and a moment for preempting the unlicensed carrier is random. Therefore, a sending moment for sending a data frame on the unlicensed carrier is random, and is discontinuous, and a timeslot for sending the data is random. That is, a timeslot sequence number is also random, and a scrambling sequence of information carried on a particular timeslot is also random, so that a receive end cannot descramble the information.